Electrolytic photographic process and its material



sH|N|cH| ToKuMoTo ETAL 3,425,916 ELECTROLYTIC PHOTOGRAPHIG PRQCESS Feb.4, 1969 AND ITS MATERIAL Filed Oct. 23, 1965 Ll In .ma Le 6L. QSQQ Qt555m 3 E mi E MSEQEQIM/ Lig/1f POSITIVE POS/T/ VE (A) NEGA TIL/E NE GAT/ VE PROCESS (A) P/eEDEVELo PME/v r PROCESS United States Patent O3,425,916 ELECTRoLYTIC PHoToGRAPHIC PROCESSv AND ITS MATERIAL Shin-IchiTokumoto, 14 2-ch0me, Fujimi-machi, Chiyodaku, Tokyo, Japan, and EijiTanaka, 25-208-go, .lapan House Corporation House, 48-1 Myojindai,Hodogayaku, Yokohama-shi, Kanagawa-ken, Japan Continuation-impart ofapplication Ser. No. 134,794, June 30, 1961. This application Oct. 23,1965, Ser. No. 503,684 Claims priority, application Japan, July 5, 1960,

35/ 30,043 U.S. Cl. 204-18 Int. Cl. B44c 1/04; B01k 3/00 ABSTRACT OF THEDISCLOSURE The present invention relates to a photographic processwherein an image of a subject matter is formed by application ofelectric current to an image-forming film unit, and photographicmaterial for use with said process.

This is a continuation-in-part of our application Ser. No. 134,794,filed June 30, 1961, now Patent 3,227,633 and is directed tophotographic processes employing monochromatic light.

It is an object of the present invention to provide an electrolyticphotographic process and photographic material for use with the processwhereby application of a very small quantity of electricity makes itpossible to obtain a picture of sufficient density. Thus, it is possibleto use such electrolytic photographic material, which is highlysensitive, while it is being handled in light.

Another object of the present invention is to directly produce acontrasting picture in a single step Without use of separation images.

A further object of the present invention is to produce a picture filmmaking use of the transfer process.

The photographic process of the present invention is such that anelectrolytic photographic process can be adapted for use in electrolyticphotography wherein an image is formed by exposure to light andapplication of an electric current, or in an electric recordingapparatus, such as telautograph, wherein an image record is made byapplication of electric current. Electric current in a quantitycorresponding to the color and luminosity of each unit area of a subjectmatter is applied to each unit area of the image-forming film unit so asto produce or reduce in the image-forming film unit, the initiatorswhich serve to accomplish or promote the chemical reaction necessary toform an image. The quantity of substance in each unit area of theimage-forming film unit is differentiated according to the color andluminosity of each unit area of the subject, so as to differentiate ineffect the extent of accomplishment or lpromotion of the chemicalreaction necessary to form an image, at each unit area of theimage-forming film unit. This manner of developing an image ischaracteristic of the electrolytic photographic process of the presentinvention. The characteristic of the electrolytic photographic materialof the 10 Claims lCe present invention is such that when electriccurrent is applied to each unit area of the image-forming film unit, ina quantity corresponding to the color and luminosity of each unit areaof the subject, the initiators, which serve accomplishment or promotionof the chemical reaction necessary to form an image, are brought intobeing at each unit area of the image-forming film unit in a quantitycorresponding to the color and luminosity of each unit area of thesubject. This accomplishment promotes the chemical reaction necessary toform an image to an extent in accordance with the quantity of initiatorsthus produced or reduced and the image of the subject can be developed.

The present invention is confined to monochrome photography. Thus, inthe present invention, use of the term color and luminosity as used inthe most broad sense, refers to a contrast ratio. The present inventionis confined and relates only to monochrome photography, i.e., black andwhite and the various shades of gray, as contrasted to so-called colorutilizing the three primary colors.

The instant invention has as its primary object, the provision of anelectrolytic photography process wherein the amount of electric currentflowing through the photoconductor is proportional to the intensity oflight, thus allowing the image to be reproduced by` the electrolysiscaused by the current and allowing further amplification by subsequentchemical development.

A further object of the present invention is the provision of anelectrolytic photographic process and material whereby the electrolyticreaction requires only a very small amount of electricity to produce theamount of initiators, or seeds needed for the development centers, andsensitivity is gained by chemical means, through chemical or diffusiontransfer development.

Other and further objects, features and advantages of the presentinvention will become more apparent to those skilled in the art from thefollowing detailed disclosure thereof and the drawings attached heretoand made a part of the present invention.

On the drawings:

FIGURE 1 is an enlarged, cross-sectional View of a system embodying theelectrolytic photographic process and its photographic materials of thepresent invention;

FIGURE 1a is an enlarged, cross-sectional view of the preferredembodiment of the present invention; and

FIGURE 2 is an enlarged, cross-sectional view of the pre-developmentprocess and development process embodying the electrolytic photographicprocess and its photographic material of the present invention.

In the present invention when reference is had to the application ofelectric current to each unit area of the image-forming film unit in aquantity corresponding to the color and luminosity of each unit area ofthe subject, such reference indicates that an electric -current haspassed through the image-forming film unit in such a manner that when aphoto image of the subject is formed on the image-forming film unit,there flows through each unit area thereof, electric current in aquantity corresponding to the color and luminosity of each unit area ofthe surbject. Since, therefore, this selective application of current,which means that different quantities of electricity are applied to eachunit area of the imageforming film unit, does form an image of thesubject, it must be closely related to the color and luminosity of eachunit area of the suibject. This selective application of current closelyrelated to the color and luminosity of the subject may be controlledeither by a photoconductive layer, photovoltaic layer, orphotorectifying layer positioned in parallel with the image-formingfilm, or it may be controlled, as in the case with telautograph, bycounter-positioned electrodes scanning over the surface of theimage-forming film.

The above-mentioned photoconductive layer may be selected from the groupconsisting of photosensitive cadmium sulfide, zinc selenide, antimonytri-sulfide, or amorphous selenium. The photovoltaic layer orphotorectifying layer is composed of such complexes as selenium andmetal foil. Further, such complexes as phototransistors, which arecomposed of heterogeneous semiconductors acting as controllers, effectthe same results.

Such complexes as mentioned above, function as a photovoltaic layer, orotherwise, being connected with an outside source of electricity in sucha manner that when they are unexposed they resist the voltage of saidsource and check the flow of the current, but can release it only whenexposed. Thus, they function as a photorectifying layer. A layer of suchcomposite material is generally low in its horizontal or sheet-wiseelectrical resistance. In such a case, the material must be divided intoa great number of points, electrically insulated one from the other, andarranged on the surface of a base.

The current to be applied to the image-forming film unit may bealternating current or direct current flowing in a definite direction.In the case of an alternating current, the current-caused reactionwhereby the initiators, which serve to accomplish or promote thechemical reaction necessary to form an image, are produced or reduced inthe image-forming film unit and need not lbe cornpletely reversible.Examples of this reaction will be discussed in Example I, which will bedescribed later.

The chemical reaction necessary to form an image is the one whereby itcan be observed that substances are so colored, faded, changed incontrast ratio, or fixed as to form an image. The chemical reaction thatmay be employed in the formation of the image may involve any of suchcases as, for example, a product of the reaction of a silver salt,copper salt, mercury salt, or lead salt with a developer having a colorand luminosity different from those prior to the reaction; or a productwherein an inorganic or organic compound is converted into a productwhic-h has a solubility different from that prior to conversion.

Following are examples of the initiators that can be used to accomplishor promote the chemical reaction necessary to form an image.

If, for example, sodium silver thiosulfate or a like substance, which iscomparatively irreducible is used alone, it undergoes little chemicalreaction which is discernible to the naked eye when it contacts suchliquid developers as are composed principally of hydroquinone. However,if silverl sulfide, lead sulfide or other heavy-metal compounds coexistwith the comparatively irreducible substance, even in a very smallquantity, then the comparatively irreducible substance becomesreducible. For example, in the case of sodium silver thiosulfate, silverwill be made free. lf, in this case, there coexists an organic couplerwith the sodium silver thiosulfate and a developer, the developeroxidizes upon reducing silver and couples with the coupler to produce acolored substance, although a non-reacted developer does not couple withsuch a coupler.

The above-mentioned sulfides or heavy-metal compounds are the substancesthat serve to accomplish or promote the chemical reaction necessary toform an image which could not proceed `without them. In other words,they represent a catalyzer or an initiator for the image-formingreaction. Examplied hereunder is the system to cause such initiators forimage-forming reaction to be produced or reduced by application ofelectric current.

Example I 744 grams of sodium thiosulfate are dissolved in 3 liters ofwater, in which solution 376 grams of silver bromide are dissolvedcompletely with stirring so as to give a solution of sodium silverthiosulfate. To this solution is added the same quantity of alcohol, soas t0 precipitate the sodium silver thiosulfate therein. The precipitatethus obtained is Washed with alcohol and dried into crystallized sodiumsilver thiosulfate. 6() grams of this crystal is added to 500 cc. of anaqueous solution of 10% gelatine. This liquid composition is spread,several microns or several tens of microns thick over a conductive base,such as NESA glass, which has a thin, transparent and semi-conductivelayer principally made of tin oxide on a surface, or a layer ofplatinum, and is then dried. While this dry coated film is `being madesuitably wet, and a movable electrode of platinum is being moved withits end contacting the surface of the coated film, current variableaccording to the image pattern is sent with the movable electrode beingmade negative. In the present example, the maximum voltage 4between theelectrodes is 7 volts, and the maximum quantity of electricity is lmicroampere second per square centimeter. The mere application ofcurrent causes no apparent change to the surface of the coated film thatcould tbe discernible with the naked eye. However, when electrolysis isconducted in an aqueous solution of sodium silver thiosulfate with aplatinum electrode, or when, in the present example, the quantity ofelectricity is increased, silver sulfide is produced discernibly at thecathode. It is obvious, therefore, that in the above-mentioned example,silver sulde is produced in such a slight quantity that it isindiscernible to the naked eye.

Over the said coated film is spread a developer comprising:

Water Cc 60 Sodium carboxymethyl cellulose grams 2.5 Sodium sulite d02.6 Sodium thiosulfate d0 01.7 Citric acid do 1.3 Sodium hydroxide do2.5 Hydroquinone do 1.7 l-phenyl-S-pyrazolidone do 0.03

Several seconds after the developer has been spread, there appears a`black image pattern corresponding to the quantities of electricityapplied. In case the coated film used in the above example is utilized,especially together with a photoconductive layer, photovoltaic orphotorectifying layer (which will be discussed later) to control thequantities of electricity to be applied, it is preferable `for theapplication of the current that the developer be positioned between thecoated film and such layer without contacting the air.

In order to preserve the image that is created on the image-forming filmin the above-mentioned example, a preservable image can be obtained bywashing away the unreacted or partially unreacted or excessivecomponents used to form the image, including silver and dyes. The imageobtained in any of the cases in the present example can be transferredto another image-receiving layer by the usual transfer process ofphotography.

In the above-discussed example, the initiators for the image-formingreaction are produced by application of electric current. The followingexample will discuss the case when such initiators are reduced byapplication of electric current.

Example II A conductive NESA glass having a thin, transparent andsemi-conductive layer principally compsed of tin oxide on its surface ora layer of platinum, is coated, by evaporation very thinly and uniformlywith silver, and this silver layer is covered with a protective layer ofpolyvinyl alcohol which is completely saponied making it insoluble incold water. This layer unit is kept in contact with an aqueous solutionof 2.0% sodium nitrate, and electric current is then applied in a mannersimilar to that described in Example I.

The layer unit is then adequately washed with water, and after washing,its protective layer is covered with a gelatine film containing sodiumsilver thiosul-fate such as described in Example I. To this gelatinfilm, the developer discussed in Example I is applied, and secondslater, the areas where current did not pass, turn black. The greater thequantity of electricity applied, the less the extent of blackeningbecause silver, an initiator for image-forming reaction, is convertedinto silver nitrate and washed away. Thus, a desired image is obtained.

Unless transfer based upon this image is desired, unnecessary orexcessive components other than those necessary for the formation of theimage will be Washed away from the layer unit. However, if desired, theimage can ybe transferred to another image-receiving layer by means ofthe usual transfer process of photography.

Thus far, the present invention has been explained primarily around thesystem of producing or reducing initiators for image-forming reaction byapplication of electric current. Initiator agents of image-formingreactions are not limited to the above-mentioned silver salt, norsubstances to initiate a reaction in the above-mentioned substances. Afurther example is: A prod-uct obtained through abrupt oxidation of amixture of 100 grams of tin chloride, 1 gram of antimony chloride, 10cc. of 35% hydrochloric acid, 1 gram of ammonium fluoride and 100 cc. ofwater being sprayed over a glass board heated above 600 C., which thoughelectrically conductive, is ineffective as an initiator for theimageforming reaction. However, a product obtained by reducing the saidproduct by electrolysis is a highly effective initiator for theimage-forming reaction. As initiators or seeds for the image-formingreaction, organic compounds as well as inorganic compounds of metal canbe used, particularly, for example, a metallic compound of pyrazole,triazole, imidazole, thiazole or thiazolidine, and derivatives of suchcompounds.

However, it is preferable that the initiators for the image-formingreaction be of a heavy metal or semiconductive material per se, or elseof heavy metal or semi-conductve material obtained through theapplication of electric current. lFurther, it is preferable to have theinitiators in the form of a galaxy, as it is thereby made easier to formhalf tones, espectially in the cases where the transfer process isemployed in making a picture.

In the case of contrasting reaction by reduced silver as in Example I,in order to make it easier for the reduced silver, which is produced bythe image-forming reaction, to grow into a size large enough to easilyabsorb visible rays, and in order to provide, beforehand, in the colloidenough room for the reduced silver to grow, it is desirable that theinitiators or seeds of the image-forming reaction, such as theabove-mentioned silver thiosulfate, be dispersed in the gel colloid in acrystal form of the desired `size and that the said initiators beproduced by application of current as a part of, or adjacent to, thespace occupied by these crystals.

The pulverized sodium silver thiosulfate or the like initiator substanceof the image-forming reaction attached to the silica aerogel discussedabove, is dispersed in oil-soluble resin, such as polyvinylbutyral, sothat it contains more than 101% of the initiator and is then spread in athin film and dried. This thin lm, being permeable to ions, is capableof having initiators for the image-forming reaction produced in thespace occupied by the above-mentioned crystals. If, to theabove-mentioned silica aerogel, or some such like substance, hydrophilicresin such as polyvinyl pyrolidone, polyvinylmethyl ether, or some suchsimilar material, or hydrophilic colloid such as gelatine, sodiumcarboxymethyl cellulose, or similar material, is attached, better ionpermeability can be obtained. In the above examples, again, theinitiators of the image-forming reaction were contained beforehand inthe image-forming film, but it goes without saying that they do notnecessarily have to be counted in the image-'forming filmI beforehand,but can be added or applied thereto at any suitable time in the courseof the image-forming process.

For convenience, in illustrating the accompanying drawing, thephotoconductive layer, photovoltaic layer, or photorectifying layer willhereafter be inclusively called photo-current-passable layer, and theinitiators of the image-forming reaction will be calledcontrast-changeable reagents.

Various systems of utilizing the photo-current-pa'ssable layer tocontrol 'the quantities of electricity to be applied are illustratedhereunder with reference to the accompanying drawings:

In the accompanying drawings, FIGURE 1 and FIG- URE 2 depict a system toobtain a mono-colored image. FIGURE lla shows the preferred form lof theinvention wherein a protector layer P and separator layer S are notnecessary. Other than these changes, Ithe film shown and numbers usedare identical to those discussed in conjunction with 'FIGUlRE 1.

lFIGURES 1, la and 2 show, respectively, the photographic material of-the present invention consisting of two blocks, block =A comprising animage-forming iilm uni-t of layers '1 to 5 combined, and block B, a unitof layers 7 to 9 combined. 'The latter block B is shown in the [figuresmerely to indicate the relative position to block A of a counterelectrode 8, which is transparent or opaque, and may be utilized inapplication of electric current in the course of the image-formingprocess, and of an image-receiving layer 7 to be used in transferringthe image. Layer 9 represents a base of paper, transparent cellulosederivatives or glass to support the electrode 8 and/or theimage-receiving layer i7. Layer 6 represents the layer of electrolyticliquid or transferring liquid to be spread between said blocks A and Bat the time of application of electric current or transferring. Layer 1Srepresents a layer containing photoelectric-sensitive contrastchangeablereagents such as sodium silver thiosulfate and couplers. Layers S and P(as shown in FIGURES 1 and 2) will be described later. Layer 3represents the photocurrent-passable layer. Layers 2 and 1 represent,respectively, the transparent or -opaque electrode and the base.

lIn FIGURE 2, the image-forming light: passes through the transparentbase 2'1 and the transparent electrode 22, and forms an image on thephotoconductive Ilayer 123. `A direct current voltage is then appliedbetween the electrode 22 and the counter-electrode 261. During thisapplication, current -flows through the layers in proportion to theintensity `of the light in the image, causing electrolysis in thereagent layer 25. Development centers or seeds are deposited on the faceo'f the protector layer 24 or on the face of the cathodiccounter-electrode that is in `close contact with the reagent layer.Then, with the -electric current open, the negative film (Z1-26) lisplaced lover the image-receiving layer 27 and its base 28 with atransfer-developer 29 between. In the course of 10 to 45 seconds,development occurs in the negative ttilm around the centers formed bythe electrolysis, and the contrast reagents that have not reacted,diffuse into the imagereceiving layer Where a positive image iis formedby development centers already present in that layer.

In 'FIGURE 1, the layer S represents a layer required with two or morecontrast-changeable reagents, such as two types of contrast-changeablereagents as sodium silver thiosulfate and a coupler, mentioned above,used separately in the order of their performing the image-formingreaction, that is, for example, this layer S contains sodium silverthiosulfate, while the layer 5 contains the couplers.

Layer P, in FIGURE i1, represents a protector layer to protect thephoto-current-passable layer 3 from the image-forming reaction. It isrequired that this layer be capable of passing electric current, andfurther that the passage of electric current be made easy layer-wise, orin a direction vertical to the layers and diiiicult sheet-wise, orhorizontally. As shown in IFIGURE l1, the layers are so divided that asthe exposing light approaches the layers from the side of thephoto-current-passable layer, the `said layer may be opaque. In thiscase, conductive paint containing carbon powder, silver powder and thelike conductors for electricity, can be used. The vertical or layer-Wiseand horizontal or sheetJwise resistance of the layer can 'be controlledby adjusting the quantity `of powder conductor contained in the paintand the thickness of the layer. Conductive paint having an ethoxy resinand containing 13% (in weight) carbon powder has, when formed in aIO-micron thick layer, a layer-wise resistance 'of 100 ohm per 1 squarecentimeter and a sheet-wise resistance of 100 megohm square, theembodiment `of which has given satisfactory results.

However, as is shown in FIGURE 1, where it is so devised that theexposing light approaches the photo-current-passable layer from ltheside of the protector layer P, the layer must be transparent. Theinventors of the present invention, intending to employ such protectorlayer, have invented the following transparent conductive paint andobtained very satisfactory results from emplying it. Five grams ofsilica aerogel are dispersed 1in a mixture of 65 cc. of water and 50 cc.of alcohol, and then added thereto and mixed adequately therewith, is 35cc. mixture of 100 grams of tin chloride, 1 gram of antimony chloride, lcc. of 35% hydrochloric acid, r1 gram of ammonium tiuoride and 50 cc. ofwater. This mixture is sprayed into a gas flame and by this heattreatment a transparent powder is produced. This powder is piled 35microns thick and spread lightly to have a vertical resistance of 80ohms per square centimeter. Ten grams of this powder is dispersed in atoluene solution of 110 grams of methyl methacrylate and is so spread ina thin film, such that the film will be 5 microns thick upon drying.Then, after drying, the film is impregnated with paraffin at 60 C. Thetransparent and conductive protector thus obtained has alight-penetration rate of more than 90% and a layer-wise resistance of80 ohms per square centimeter and a sheet-wise resistance of 100 megohmssquare.

As set forth below, the image-receiving layer is explained for thepurpose of transferring the image.

In the present invention, when an image is to be transferred, thevarious known methods of transfer photography can be adopted. It ispreferable that the previously mentioned color-changeable reagentsremaining nonreacted within the image-forming film unit be made to passthrough the transfer liquid layer 6 and be reacted on theimage-receiving layer 7 to form a picture. If, for example, the reactionto reduce silver `from a silver salt is utilized for the image-formingreaction and if the image-receiving layer has initiators for theimage-forming reaction in it before the reduction reaction occurs, thenthe image-forming reaction will proceed immediately in those placeswhere the color-changeable reagents are present. An example of theimage-receiving for the purpose of transferring the image is:

Silica aerogel grams Water solution of 2% sodium sulfide cc 140 Cadmiumacetate grams 1.5 Lead acetate do 0.1 Zinc nitrate do 1.5

It is obvious, of course, that development on the imagereceiving layercan be conducted independently, after the transfer of color-changeablereagents to the image-receiving layer has been completed.

Methods for the production of the photocurrent-passable layer are, byway of example, described in the following discussion.

A mixture consisting of a photo-conductive cadmium sulfide powdercontaining, in molar ratio, copper as an activator in quantities ofone-ten thousandth of cadmium sulfide, the similar ethoxy resin ashereinbefore set forth in an amount of 4% by weight of the sulfidepowder and a diacetone alcohol (solvent) of a suitable amount, whichmixture is then uniformly coated on the surface of an electrode, as forexample, NESA glass to make a laminate having a thickness, as forexample, of about microns. When a potential of volts is transversely orlayerwise imposed on this laminate, and the laminate is exposed to thelight of about five-foot candles, a photocurrent of about 18`milliamperes per square centi-meter develops. If the exposure is cutoff, there is almost no flow of current. Further, in place of theabove-mentioned photoconductive cadmium sulfide, a photosensitive powdercan be utilized which consists of, for example, two kinds ofsemi-conductive material which may be described as follows. Aphotosensitive powder is produced, for example, by precipitating acuprous oxide (a semi-conductive material) from an aqueous solution ofcopper salt mixed with a reducing agent such as grape sugar on thesurface of cadmium sulfide powder (another semiconductive material)containing, in 'molar ratio, fixe-ten thousandths of indium. Then byheat treating the thus obtained powder in an atmosphere of an inactivegas at a temperature of about 550 C. for a very short period of time, asuitable powder is obtained. The powder is then mixed with the resin inthe same manner as that hereinbefore set forth and the resulting mixtureis coated on the surface of an electrode to make a laminate having athickness of about 40 microns. When a potential is imposed on thislaminate under the same conditions as those described before, aphotocurrent of about 7 milliamperes/cm.2 develops under the irradiationof about five-foot candles, and if the irradiating rays are cut off,only a current of 3 10-4 of the current can be obtained.

Further, a photocurrent-passable layer of the following type may causean available current to pass therethrough under a low potential. Such aphotocurrent-passable layer can be produced in the following manner.

A nickel-plated electrode is applied to the surface of network glassplate which has a thickness of about 0.4 millimeter and has regularlybeen formed on the overall surface thereof with numerous perforations,these perforations being filled with selenium. The surface thereof ispolished and the glass plate thus obtained is heated at a temperature ofabout 200 C. for 4 hours and then cooled slowly. Another network glassplate, which has the same size of perforations in the same position asthat previously described, is used as a shadow mask, and cadmium andgold are thinly deposited on only the surfaces of the selenium particlesinsulated by the glass network, by a spattering process and vapordeposition process, respectively, and thus, the desiredphotocurrent-passable layer is obtained.

The photosensitivity of the photocurrent-passable layer thus produced isshown as follows.

The gold portion of the above-mentioned photocurrentpassable layer iselectrically connected to a copper electrode of an electric cell whichcomprises electrodes of copper and aluminum and an electrolyte solutionof 5% aqueous sodium chloride solution, and the nickel portion of thephotocurrent-passable layer is also connected to the aluminum electrode.When the layer is exposed to the light of 1Z0-foot candles, photocurrentof 0.1 milliampere/em.2 can be obtained, and when the exposure is cutoff, the current substantially ceases to flow.

In place of the copper-sodium chloride solution-aluminum cell, a layerhaving an electric cell structure, in which metals having a differentpotential are placed on both sides of the color-changeable reagent layerin such a menner that the metals embrace the reagent layer between them,can be used in combination with the abovementioned photocurrent-passablelayer.

Of course, it will be understood that the above described process andmaterials, including the quantities thereof, arrangements of parts,etc., are given merely by way of example and not by way of limitation.Modifications and variations may be made in the above product andprocess without departing from the scope of the invention hereindescribed. Such technically comprehensible changes, as for example,wherein two or more types of color-changeable reagents are separatelycontained in the layers and S as shown in FIGURE 1. Further, a protectorlayer or diffusion-controlling layer may be created to be positionedbetween 5 and S for the purpose of delaying the diffusion time of someof the color-changeable reagents so as to control the time and order ofthe colorchangeable reagents reaction in the image-forming process.

By use of the term photo-electric-sensitive contrastchangeable reagentswe mean a chemical which will not react to light or electricity alone toproduce a different contrast ratio, but rather one that must have asubstantially simultaneous `application of elecricity and light toproduce a different contrast ratio. The term colorchangeable reagent asused herein means substantially the same as photo-electric-sensitivecontrast-changeable reagents.

Thus, it will be understood that modifications and variations may beeffected without departing rom the scope and spirit of the novelconcepts ofthe present invention.

We claim as our invention:

1. In a black and white pi-cture film for photosensitization with anenergy source including `a light source for monochromatic light, thecombination consisting essentially of, (l) a layer containingphoto-electric-sensitive contrast changeable reagents for at least twodifferent contrast ratios and initiators for picture forming chemicalreactions which are produced by the application of electric current,said initiatiors being selected from the group consisting of heavy metalsalts, tin oxide, platinum and a product obtained throughelectrolysis-reduction of a mixture of tin chloride, antimony chloride,hydrochloric acid, ammonium fiuoride and water, (2) a layer useable asan electrode for electric current corresponding to an objective image tobe reproduced, and (3) means for providing said elect-ric current.

2. A picture film ias defined in claim 1 wherein said initiators areheavy metal salts obtainable by the application of electric current.

3. A picture film as defined in claim 1 wherein said initiators aresemi-conductors obtainable by the application of electric current.

4. A picture film xas defined in claim 1, wherein the initiator is tinoxide.

5. A picture film as defined in claim 1 wherein the initiator is leadsulfide.

6. A picture film as defined in claim 1, wherein the initiator issodiurrr silver thiosulfide.

7. In a black and White picture film for photosensitization with anenergy source including a light source for monochromatic light, thecombination consisting essentially of a layer of transparent supportfilm, a second layer useable as an electrode for an electric currentcorresponding to an objective image to be reproduced, a third layercontaining photo-electric-sensitive contrast changeable reagents andinitiators therefore which are actuated to form a latent image by thecombination of light and electric current, said initiators beingselected from the group consisting of heavy metal salts, lead sulde,sodium silver thiosulfide, tin oxide, platinum and a product obtainedthrough electrolysis-reduction of a mixture of tin chloride, antimonychloride, hydrochloric acid, ammonium fluoride and water, which productis sprayed on an inert substrate heated above 600 C., said third layerbeing upon the receiving layer which contains a counterelectrode with asupport film, and a fourth layer of an electrolyte being insertedbetween said third and receiving layers.

8. In a photographic image-forming method consisting essentially ofproviding an actinic light source, a pair Of electrodes lying ingenerally parallel planes, :a photo-current-passable mosaic elementlying in va generally parallel plane :between the electrode planes andhaving a layer interposed between the mosaic element and" one of saidelectrodes, said layer containing photo-electric-sensitive contrastchangeable reagents which are coextensive and initiators therefore whichare actuated to form a latent image by the combination of light andelectric current, said initiators being selected from the groupconsisting of heavy metal salts, lead sulfide, sodium silverthiosulfide, tin oxide, platinum and a product obtained throughelectrolysis-reduction of a .mixture of tin chloride, antimony chloride,hydrochloric acid, ammonium fiuoride and Water, means for creatingelectric potential across the electrodes, and selectively exposingportions of said mosaic to actinic light and an electric current tocreate a latent image thereon, subsequently developing said latentim'age to formI a visible image.

9. In a black and white picture film for photosensitiz-ation with anenergy source including a light sounce for monochromatic light, thecombination consisting essentially of a layer containing photo-electricsensitive contrast changeable reagents for at least two differentcontrast ratios and heavy metal salt initiators for picture formingchemical reactions which are produced by the application of electriccurrent, a layer useable as an electrode for electric currentcorresponding to lan objective image to be reproduced, and means forproviding said electric current.

10. In a black and white picture film. for photosensitization with anenergy source including a light source for monochromatic light, thecombination consisting essentially of a layer containingphoto-electric-sensitive lcontrast changeable reagents for at least twodifferent contrast ratios and semi-conductor initiators obtained throughelectrolysisreduction of a mixture of about grams of tin chloride, about1 graml of Aantimony chloride, about 10 cc. of 35% hydrochloric acid,about 1 gram of ammonium fiuoride and about 100 cc. of water, whichinitiator is sprayed on :a glass board heated above 600 C.

References Cited UNITED STATES PATENTS 1,918,492 7/1933 Schmidt 204--23,142,562 7/1964 Blake 96--1 3,227,633 1/ 1966 Tokumoto et al 204-2ROBERT K. MIHALEK, Primary Examiner. W. VAN SISB, Assistant Examiner.

U.S. Cl. X.R. 96-1

